Weather Data

Surface Heat TransferRed Calc Tool User Guide

What this tool can do for you

This tool is most often used to find heat transfer through a surface,
but because it is a solve-all tool, you may solve for any one of the
five values.

Calculated values

Heat transfer; or

Temperature difference; or

R-value; or

Time interval; or

Area.

Tips

Clicking the label for any input or result will cause a
popup help box to appear. This help box includes the
allowed and normal values (for inputs).
Read more.

Because this is a solve-all tool, you may find a result for any one of the
five values. Click the radio button to the left of the value label to
solve for that value. When you check a radio button to solve for a
value, the color of the label changes from black to blue.

This tool is most often used to solve for "Heat transfer", the last
of the five values.

With this tool you can calculate annual heat loss/gain through a surface
by entering "1 day" for the time and then entering the number of heating degree
days for the temperature difference. You will receive a warning message
indicating that your temperature difference input is outside the normal
range, but you may proceed with the calculation.

Inputs and field measurements

Surface area - measured in field.

R-value (or 1/U-factor) - determined in field.

Time interval - usually one hour to correspond with heat transfer period used
for sizing heating or cooling systems.

Temperature difference - the temperature difference from one side of a
surface to the other, often the temperature difference between indoors
and outdoors on a design temperature day.

Background

It is probably easiest to think of heat transfer through a three dimensional
object, like a house window, as being characterized by conduction only. However
heat transfer
through building parts is usually a combination of conduction, convection,
and radiation. The part that each of these plays is represented by the rated
R-value of the building part, for example, the complex heat transfer through
fiberglass insulation is represented by a R-value of 3.2 per inch (RSI of 0.564).

This RED Calc tool is based on one of the two basic equations used for sizing heating and
cooling systems for dwellings. The other equation calculates hourly heat loss
or gain attributed to air leakage.

Manual J: Residential Load Calculation, 7th ed. (1986). Air Conditioning
Contractors of America. Washington, DC.
Comment: The "bible" for calculating heat loss/gain
in dwellings. Includes R-value tables and other useful data. Much simpler
than the 8th edition. If you only want the basics without the bushels
of details, purchase the 7th edition.

Manual J: Residential Load Calculation, 8th ed. (2003). Air Conditioning
Contractors of America. Washington, DC.
Comment: The "bible" for calculating heat loss/gain
in dwellings. Includes R-value tables and other useful data. Much more
complex, but more accurate than the 7th edition. If you want all the details,
purchase the 8th edition.

Mott-Smith, Morton. 1962. The Concept of Heat and its Workings Simply
Explained. Dover Publications, Inc. New York.
Comment: Great classic text on the subject of heat and
heat transfer.